HAEMOGLOBIN PHYSIOLOGY

PHYSIOLOGY OF HEMOGLOBIN

1. HEMOGLOBIN Prepared by Fatima sundus

2. Four Hgb chains bind together loosely to form the entire hemoglobin molecule. The different types of chains are designated as alpha (α ) beta (β ) ( γ) gamma (δ ) delta chains.

3. The synthesis of hemoglobin begins in the proerythroblasts and continues even into the reticulocyte stage of the RBCs.

4. Hemoglobin is the main protein in mature red blood cells. Each RBC contains over 600 million hemoglobin molecules.  It is tetramer, that is, one molecule of hemoglobin in adult is composed of four globin chains , 2 alpha and 2 beta.  These chains are derived from chromosome, mainly chromosome 16 and 11 .

5. It carries oxygen from the lungs, where blood is oxygenated, to body cells. When saturated with oxygen, hemoglobin is called oxyhemoglobin

6. Carboxyhemoglobin a compound formed in the blood by the binding of carbon monoxide to hemoglobin. It is stable and therefore cannot absorb or transport oxygen

7. Carbaminohemoglobin  ( carbaminohaemoglobin BrE ) (CO2Hb), also known as carbhemoglobin and carbohemoglobin ) is a compound of hemoglobin and carbon dioxide

8. in addition to oxygen and carbon dioxide, hemoglobin takes up and releases a third gas, nitric oxide . Nitric oxide plays an important role in regulating blood pressure by relaxing the blood vessel walls, thus increasing blood flow.

9. Hemoglobin is contained entirely in the red blood cells, amounting to perhaps 35 percent of their weight . To combine properly with oxygen, red blood cells must contain adequate hemoglobin. Hemoglobin , in turn, is dependent on iron for its formation . A deficiency of hemoglobin caused by a lack of iron in the body leads to anemia.

10. Hemoglobin carries more than 20 times its volume of oxygen. Some chemicals, such as carbon monoxide, combine so firmly with hemoglobin that it can no longer combine with oxygen.

11. After a life of perhaps 120 days , red blood cells are destroyed in the spleen , or in the course of circulation, their hemoglobin is broken into its constituents, including iron, which enters new blood cells formed in the bone marrow.

12. When blood vessels rupture, as in an injury, the red cells are released and escape into tissue, where they are broken down. The hemoglobin is converted into bile pigments, the color of which is responsible for the appearance of bruises.

13. Alterations in the structure of hemoglobin can lead to life-threatening illnesses. The most important of these conditions is sickle-cell anemia , which involves a hereditary change in one of the amino acids that make up hemoglobin . The thalassemia's are a group of hereditary diseases of similar origin sickle cell anemia, the amino acid valine is substituted for glutamic acid at one point in each of the two beta chains. When this type of hemoglobin is exposed to low oxygen, it forms elongated crystals inside the RBCs that are sometimes 15 micrometers in length .)

14. Haemoglobin ( Hb ), protein constituting 1/3 of the red blood cells Synthesis begins in proerythroblast 65% at erythroblast stage 35% at reticulocyte stage Two parts Haem Globin

15. Haem & globin produced at two different sites in the cells Haem in mitochondria Globin in ribosome

16. HEMOGLOBIN FORMATION the basic chemical steps in the formation of hemoglobin First , succinyl -CoA , which is formed in the Krebs metabolic cycle binds with glycine to form a pyrrole molecule . In turn, four pyrroles combine to form protoporphyrin IX , which then combines with iron to form the heme molecule. Finally , each heme molecule combines with a long polypeptide chain, a globin synthesized by ribosomes, forming a subunit of hemoglobin called a hemoglobin chain

17. Each chain has a molecular weight of about 16,000; four of these chains, in turn, bind together loosely to form the whole hemoglobin molecule.

18. During the various stages of life such as embryonic, fetal and adult stages, different globin chains are expressed. During the fetal period, from about two months until birth , the dominant globin chain is alpha and gamma and this is known as fetal hemoglobin ( HbF ). However, shortly after birth about 3-6months, one will notice a fall in fetal hemoglobin ( HbF ) and a there will be a rise in adult hemoglobin ( HbA ). An alteration to the alpha or beta globin will result in an abnormal hemoglobin.

19. FUNCTIONS The major role of hemoglobin is to carry oxygen from the lungs to the tissues and return carbon dioxide (CO 2 ) from the tissue to the lungs . It is the oxygen carrying component of RBCs.  Oxygen binds to hemoglobin with high affinity in an oxygen-rich environment and leaves hemoglobin in an environment where there is not enough oxygen.

20. Normal Range of Hb . For  females the normal range for hemoglobin is : 11.5-15.5 g/dl For  males the normal range for hemoglobin is : 13.5-17.5 g/dl

21. Conc of Hb in RBC RBCs can concentrate maximum Hb upto 34 gms per 100ML Of Blood . OXYGEN BINDING POWER OF Hb : MALE : 100 ml of Blood( 16gm ) can carry 21 ml of oxygen . FEMALE : 100 ml of blood( 14gms ) can carry 19 ml of oxygen.

22. TYPES OF HAEMOGLOBIN HbA ( Alpha2 Beta2) HbA2 ( Alpha2 Delta2) HbF ( Alpha2 Gamma2) Gower I ( Zeta2 Epsilon 2 ) Gower II (Alpha2 Epsilon 2)